Preparation And Characterization Of A Potential Thin Solar Cell Absorption Material CuYSe₂

Copper indium gallium selenide?CIGS?is one of the thin film solar cells which has been commercialized application.However,rare scattering elements of indium?In?and gallium?Ga?increase the cost and limit its wide-scale application for CIGS solar cells.Rare earth element yttrium is cheaper and much more abundant compared with In and Ga in China.In this work,the substitution of indium and gallium by yttrium,a new kind of absorber materials CuYSe₂ was proposed.In addition,the structure,reaction mechanism and photoelectric property of CuYSe₂ have been thoroughly studied.Firstly,the electronic structure and optical properties of CuYSe₂ have been clarify based on the first principles,using the Materials Studio software.It has been found that CuYSe₂ has suitable band gap of 1.533 eV and high absorption coefficient?more than 105 cm-1?.Such results proved that the CuYSe₂ is very suite for the absorption material of thin film solar cells.Secondly,the CuYSe₂ has been synthesized by self propagating high-temperature synthesis?SHS?method.It has been found that the SHS process can be divided into four stages.They are preheating stage,plateau stage,SHS reaction stage and cooling stage.The ignition temperature and the highest temperature of SHS is 359.2 ? and 1112.5 ? in our experiment,respectively.The first stage is ascribed to the reaction between Cu and Se,and the second stage is Y-Se and Cu-Y-Se with a reaction rate of 1.2 mm/s.The main effect of molding pressure is preheating time,maximum temperature,reaction rate,the surface morphology,and the powder particles of CuYSe₂ and the optimal molding pressure is 5 MPa.It has been found that the surface morphology and band gap are related to the ratio of Se in raw materials and the optimal ratio is 1:1:2.05.A photoelectric device with the structure of Glass/CuYSe₂/Ag was fabricated by spin coating.The ILight/IDark of the device is 3.6 at the bias voltage range of-IV-IV.The post selenium heat treatment are applied to clarify the effect on CuYSe₂ film under different temperature.It has been found that the best temperature is below 300 ?.Surface modification by alkali ions are adopted to CuYSe₂ films.The results show that 1000 times raise of current density has been achieved and different alkali ions has different effects.It has been found that Li+can obtain highest opto-current density,and K+ can obtain high growth rate during 50 s illumination?AM 1.5?while Rb+ can obtain the opto-current density and growth rate after Li+ and K+ respectively.p-YCuOSe with a band gap of 2.05 eV has been synthesized by rapid solid-phase method at 500 ? for 60 min.The film exhibited a resistivity of 3.3×10-3 ?·cm and carrier concentration of 6.25×10¹⁶cm^-3.